As a process for preparing tetrafluorobenzene carbaldehyde alkyl acetals, there has been heretofore disclosed, for example, a preparation process comprising reducing tetrafluorodicyanobenzene by the use of a sponge nickel catalyst (patent document 1, non-patent document 1). According to these documents, the desired product can be prepared, but sponge nickel that is a catalyst is added into sulfuric acid, so that the catalyst is dissolved and the catalytic amount is increased. Further, the catalyst thus dissolved cannot be used repeatedly. Moreover, there resides a problem that the reaction yield is not so high. As another process for preparing tetrafluorobenzene carbaldehyde, a process comprising performing reduction and hydrolysis of tetrafluorodicyanobenzene using a sponge nickel catalyst in the presence of water (patent document 2) has been disclosed. Also in this process, reaction is carried out in sulfuric acid using sponge nickel as a catalyst, and therefore, the same problem takes place.
Patent document 1: pamphlet of International Publication WO00/68173
Patent document 2: Japanese Patent Laid-Open Publication No. 158754/2001
Non-patent document 1: Journal of Fluorine Chemistry, Vol. 125, pp. 451-454, 2004